Delivery of dissolved ozone

ABSTRACT

An apparatus and method for delivering ozone to a workpiece. In one embodiment, fluid is sprayed onto a workpiece placed in an ozone-rich environment. Alternatively, ozone is mixed with the fluid prior to spraying the fluid onto the workpiece. When spraying the fluid, the invention pulses the fluid at desired rates to create a substantially uniform layer of ozone-rich fluid on the workpiece. In another embodiment, the workpiece is also slowly rotated during at least a portion of the time the layer of ozone-rich fluid is applied to the workpiece.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates in general to semiconductor surfacepreparation, and in particular to the use of dissolved ozone to performcleaning, etching, and stripping operations.

[0003] 2. Background

[0004] During the wafer fabrication process, manufacturers found ozoneto be a particularly useful active reagent. For example, manufacturersuse ozone in at least the operations of sterilizing process chambers andwafers, etching oxides, stripping off photoresist material, and thelike. For example, in one approach for removing photoresist from aworkpiece, a manufacturer uses ozone to loosen undesired portions ofphotoresist. The manufacturer then washes the undesired portions ofphotoresist from the workpiece.

[0005] Because manufacturers repeat these operations many times in orderto form complex semiconductor devices, it is important to maximize theefficiency of the ozone reaction with a workpiece, thereby increasingthe speed of overall wafer fabrication. One way to increase theefficiency of the ozone reaction is to increase the overall amount orconcentration of ozone that reaches the workpiece.

[0006] The concentration of ozone reaching the workpiece is adverselyaffected by, among other things, ineffective transport of ozone to theworkpiece and interfering byproducts of the ozone reaction. In order toovercome such adverse affects, manufacturers discovered that water notonly acts as a transport solution, but also washes away the interferingbyproducts of the ozone reaction. Accordingly, manufacturers began usingimmersion tanks for operations that involved ozone reactions. Ingeneral, immersion tanks immerse the workpiece in a solution, e.g.,ozone-enriched water, in order to provide ozone reactions. However,immersion tanks provide less efficient ozone transportation becausealthough water does transport ozone, water also quickly decomposes someof the ozone into a useless solution. Therefore, water generally has anupper limit on a steady state of ozone concentration. In addition,immersion tanks do not wash away the interfering byproducts efficientlybecause the solutions in immersion tanks are relatively stable.

[0007] Therefore, manufacturers developed a “spin and spray” process inorder to overcome the drawbacks of immersion tanks. In the spin andspray process, manufacturers spin the workpiece at high velocities whilespraying water onto the workpiece in an ozone-enriched ambient. Thevelocity of the spinning workpiece controls the thickness of a waterboundary layer formed thereon. By controlling the thickness of the waterboundary layer, the manufacturers attempted to reduce the ability of thewater to decompose the ozone before the ozone could reach the workpiece.This reduction in the ability of the water to decompose ozone helpsprovide ozone concentrations above the typical limit of the water.

[0008] However, the spin and spray process has a variety of drawbacks.For example, in order to provide the desired water boundary layerthickness, the workpiece needs to spin at velocities greater thanapproximately 800 rpm. Such spinning requires a large amount ofmechanical complexity and poses a significant risk of damage to theworkpiece. While mechanical complexity greatly increases the cost of theprocess chamber, damage to the workpiece lowers yield rates.

[0009] All of the above mentioned drawbacks give manufacturers theundesirable choice between using a low concentration of ozone, therebysubstantially slowing overall wafer fabrication, or increasing theconcentration of ozone, thereby greatly increasing the overall cost andrisk.

SUMMARY OF THE INVENTION

[0010] One aspect of the invention is to provide an apparatus and methodfor delivering highly concentrated dissolved ozone to a workpiece inorder to increase the ozone reaction therewith. According to oneembodiment, the apparatus includes a process chamber employing an arrayof spray nozzles that spray a thin water boundary layer onto theworkpiece. The water boundary layer transports ozone from the ozone-richambient to the workpiece. According to this embodiment, the workpiece isheld substantially stationary.

[0011] According to another embodiment, fluid is pulsed through thespray nozzles. According to yet another embodiment of the invention, thepulsing of the water comprises a limited duty cycle. According to yetanother embodiment, the wafers are slowly rotated to ensure the waterboundary layer on the workpiece is sufficiently uniform.

[0012] The pulsing of water through the spray nozzles advantageouslyincreases the water's ability to wash away the interfering byproducts ofthe ozone reaction without increasing the overall amount of water used.This is advantageous because it allows the water boundary layer on thewafers to be very thin. The thin water boundary layer transports ozonefrom the ozone-rich ambient to the workpiece without supplying enoughwater to detrimentally decompose the ozone. Thus, highly concentrateddissolved ozone reacts with the workpiece without including thedrawbacks of mechanical complexity and risk associated with the spin andspray process.

[0013] In one embodiment, an apparatus comprises a pulsator that pulsesa solution into an ozone-rich environment to create an ozone-richsolution. In another embodiment, an apparatus comprises a sprayer thatperiodically pulses an ozone-rich solution onto a wafer.

[0014] In yet another embodiment, an apparatus comprises a rotatingplatform that is configured to rotate the workpiece. The apparatusfurther comprises a pulsator that pulses a solution into an ozone-richenvironment to create an ozone-rich solution on the workpiece. In anadditional embodiment, the apparatus pulses an ozone-rich solution ontothe workpiece.

[0015] One aspect of the invention relates to a method for stripping alayer from a semiconductor wafer. The method comprises introducing ozoneinto a process chamber and activating a water spray for a firstpredetermined amount of time, thereby creating a water layer on asemiconductor wafer, wherein the water layer transports highconcentrations of the ozone to the semiconductor wafer. The methodfurther comprises deactivating the water spray for a secondpredetermined amount of time, thereby controlling a thickness of thewater layer; and re-activating and re-deactivating the water spray untilthe ozone substantially removes portions of the layer from thesemiconductor wafer.

[0016] Another aspect of the invention relates to an ozone shower systemthat comprises an ozone source. The ozone source is configured to supplyozone to a process chamber. The ozone shower system also comprises asprayer connected to a fluid source such that fluid sprays over aworkpiece in the process chamber. The ozone shower system furthercomprises a pump connected to the fluid source, and a selector valveconnected to the pump. The selector valve is configured to selectivelypulse the fluid through the sprayer.

[0017] An additional aspect of the invention relates to a method thatcomprises introducing a reagent to an ambient and activating a solutionspray in the ambient for a first time period. The method also comprisesdeactivating the solution spray for a second time period, therebyincreasing the efficiency of a reaction of the reagent and a workpiece.

[0018] Another embodiment of the invention is a reaction chamber thatcomprises a gas input and a plurality of nozzles connected to a nozzlemanifold. The reaction chamber further comprises a wafer cartridge thatholds wafers. The reaction chamber also comprises a first fluid lineconnected to the nozzle manifold. In addition, a second fluid line isconfigured to divert water flow away from the first water line.

[0019] Yet another embodiment of the invention is a reaction chamberthat comprises at least one nozzle connected to a fluid supply whereinthe nozzle is configured to pulse fluid onto a workpiece. The reactionchamber also comprises a rotator that rotates the workpiece at avelocity ranging from approximately 100 rpm to stationary.

[0020] Another aspect of the invention relates to an apparatus thatcomprises at least one wafer-processing chamber wherein an ozone richenvironment exists within the wafer-processing chamber. The apparatusfurther comprises a sprayer, and a pulsating fluid source. The pulsatingfluid source is configured to pulse a solution through the sprayer intothe ozone rich environment.

[0021] An additional aspect of the invention relates to an apparatusthat comprises at least one semiconductor processing chamber and apulsating fluid source. The pulsating fluid source is configured topulse an ozone-rich solution into the semiconductor processing chamber.

[0022] Yet another aspect of the invention relates to a method thatcomprises introducing a reagent into an ambient, and pulsing a solutionspray in the ambient, thereby increasing the efficiency of a reaction ofthe reagent.

[0023] Another embodiment of the invention relates to an ozone showersystem that comprises a process chamber and a pump. The pump isconnected to the process chamber and configured to pulse a solution intothe process chamber.

[0024] For the purposes of summarizing the invention, certain aspects,advantages and novel features of the invention have been describedherein above. Of course, it is to be understood that not necessarily allsuch advantages may be achieved in accordance with any particularembodiment of the invention. Thus, the invention may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein. Other aspects andadvantages of the invention will also be apparent from the detaileddescription below and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is described in more detail below inconnection with the attached drawings, which are meant to illustrate andnot to limit the invention, and in which:

[0026]FIG. 1 illustrates a flow diagram of a pulsing process accordingto one embodiment of the invention;

[0027]FIG. 2 illustrates a schematic of an ozone shower system, inaccordance with another embodiment of the invention;

[0028]FIG. 3 illustrates a process chamber of FIG. 2;

[0029]FIG. 4 illustrates a chamber lid of FIG. 3; and

[0030]FIG. 5 illustrates a rotation mechanism of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] While illustrated in the context of using ozone to stripphotoresist from a semiconductor wafer, the skilled artisan will findapplication for delivery of highly concentrated dissolved ozone in awide variety of contexts. For example, the disclosed delivery of highlyconcentrated dissolved ozone has utility in many cleaning, etching, andstripping processes involved in the fabrication of a wide variety ofworkpieces. For example, the delivery of highly concentrated dissolvedozone has utility in PC Board fabrication and the like.

[0032]FIG. 1 illustrates a flow diagram of a pulsing process 10according to one embodiment of the invention. According to the pulsingprocess 10, Step S1 introduces a reagent into an environment where thereagent can react. Step S2 activates a solution spray. Step S3deactivates the solution spray. Decision S4 determines if enough timehas elapsed to substantially complete a desired reaction. If enough timehas elapsed, the pulsing process 10 ends. However, if more time isrequired, the pulsing process 10 returns to Step S2, activates thesolution spray, and repeats the steps disclosed above.

[0033] According to one embodiment, the reagent is ozone beingintroduced into the environment for any of a wide variety of reasons.For example, in the semiconductor fabrication industry, the ozone couldbe used to clean or sterilize the workpiece. The ozone could also beused to etch a semiconductor layer on, or strip another layer from theworkpiece. According to one embodiment, the ozone strips a photoresistlayer from the semiconductor wafer.

[0034] In addition, according to an embodiment of the invention, thesolution includes deionized water. The deionized water acts both as acarrier of the ozone to the semiconductor wafer and as a cleaningsolution for the byproducts of an ozone-photoresist reaction.

[0035] Thus, cycling through Step S2 (activation), Step S3(deactivation), and Decision S4, the water spray is pulsed over thephotoresist. The pulsing of the water establishes at least the followingadvantageous characteristics. First, the pulsing of the wateradvantageously provides less overall water to the photoresist. Lesswater creates a water boundary layer on the photoresist, therebyallowing the ozone to supersaturate the water above the water's normalozone concentration capacity. This supersaturation, or highlyconcentrated dissolved ozone, increases the amount of ozone reaching thephotoresist, thereby dramatically decreasing the time needed for theozone to react with substantially all of the photoresist.

[0036] Second, the pulsing of the water increases its ability to washaway or remove the leftover and interfering byproducts of theozone-photoresist reaction. For example, the water boundary layer pulsesfrom the activation and deactivation of the spray. The pulsing helpsloosen and break “chunks” of photoresist from the semiconductorsubstrate. The water boundary layer then washes away the chunks frominterfering with further ozone-photoresist reactions, thereby increasingthe effectiveness of the already highly concentrated dissolved ozonereaching the semiconductor wafer.

[0037] Accordingly, the pulsing process 10 decreases the time needed tosubstantially strip photoresist from the semiconductor wafer. Thedecrease in time advantageously speeds overall semiconductor fabricationprocess flows, thereby decreasing the overall cost of fabrication.

[0038] For example, according to one embodiment, the pulsing process 10includes a duty cycle and a pulse rate. The duty cycle is the ratiobetween the time the water spray is activated, e.g., StepS2, and thecycle time, e.g., StepS2+StepS3. On the other hand, the pulse rate isthe inverse of the cycle time, i.e., $\frac{1}{{StepS2} + {StepS3}}.$

[0039] According to one embodiment, the pulsing process 10 employs a 20%duty cycle. In this embodiment, approximately 5 seconds of water sprayactivation and is followed by approximately 20 seconds of water spraydeactivation. Therefore, the pulse rate is approximately one pulse every25 seconds.

[0040] By employing this pulse rate and duty cycle to the pulsingprocess 10, the time needed to substantially strip photoresist from thesemiconductor wafer is dramatically decreased. For example, using aconventional constant spray process, approximately 12.6 k Å of hardbaked (130° C. for 90 sec.) 10i photoresist can be substantiallystripped from a selection of semiconductor wafers in 20 minutes.However, when the above-disclosed pulsing process 10 is employed, thesame 12.6 k Å of 10i photoresist is substantially stripped from theselection of semiconductor wafers in just 5 minutes.

[0041] In other embodiments, the pulsing process 10 employs a 50% dutycycle wherein one second of spray activation is followed byapproximately one second of water spray deactivation. Therefore, thepulse rate is approximately one pulse every 2 seconds. In yet otherembodiments, the pulsing process 10 employs approximately an 8% dutycycle wherein five seconds of spray activation is followed byapproximately sixty seconds of water spray deactivation. Therefore, thepulse rate is approximately one pulse every 60 seconds. The skilledartisan will recognize that pulse ranges can vary over a wide rangeincluding, but not limited to, approximately one pulse per minute to asmany as 30 pulses per minute. In addition, the skilled artisan willrecognize that the duty cycles can range from 3 percent up to 97percent.

[0042] In one embodiment, the temperature of the water is heated fromapproximately 60° C. to approximately 95° C. In other embodiments, thewater is maintained at an ambient temperature of approximately 20° C. Inyet other embodiments, the water is maintained at sub-ambienttemperatures less than 20° C. Thus, the temperature of the water can becalibrated to a wide range of temperatures including, but not limited tofrom less that 20° C. to more than 95° C.

[0043]FIG. 2 illustrates a schematic of an ozone shower system 15 inaccordance with one embodiment of the invention. The ozone shower system15 includes a process chamber 20 having a chamber lid 25, a full chamber30, and a short chamber 35. A pump 40 pumps water from the full chamber30 to a heater 45. As the water passes through the heater 45, the heater45 raises the water temperature to desired levels. The water thentravels through a flush valve 50. The flush valve 50 allows for theaddition of water to the ozone shower system 15. The water then flowsthrough a filter 55 and on to a selector valve 60. The selector valve 60directs the water into one of two paths. The filtered heated waterdirected through the first path travels to the chamber lid 25 andeventually to the full chamber 30. Thus, the water in the first pathcompletes a water cycle from the full chamber 30, through the pump 40,through a first path, and back to the full chamber 30.

[0044] On the other hand, the selector valve 60 could also direct thefiltered heated water through a second path. The filtered heated waterdirected through the second path travels to a drain valve 65. The drainvalve 65 allows for excess water removal from the ozone shower system15. The filtered heated water in the second path then travels to theshort chamber 35. After the short chamber 35 fills with water, excesswater spills over into the full chamber 30. Thus, the water in thesecond path also completes a water cycle from the full chamber 30,through the pump 40, through the second path, and back to the fullchamber 30.

[0045] Also illustrated in FIG. 2 is an ozone source. The ozone sourcesupplies ozone to the ambient in the full chamber 30 through the chamberlid 25. Thus, according to the embodiment illustrated in FIG. 2, theozone shower system 15 circulates water through the first or second pathwhile an ozone rich environment exists in the full chamber 30. In otherembodiments, the ozone from the ozone source is injected into the fluidin the first path, the second path or both paths. The injected ozonecreates an ozone rich fluid that is applied to a workpiece as describedin further detail below.

[0046] According to one embodiment of the invention, the pump 40 is abellow pump commercially available from White Knight Fluid Handling,Inc. The heater 45 is an in-line heater commercially available fromSanta Clara Plastics. In addition, the flush valve 50, the selectorvalve 60 and the drain valve 65 are three-way valves commerciallyavailable from Fluoroware. The filter 55 is an inert particle filtercommercially available from Pall Corporation.

[0047] According to one embodiment, the ozone source is an Astex 8200Ozone Generator configured to peak performance recommendations by themanufacturer. For example, the oxygen and nitrogen supplies are set tosupply approximately greater than 13 percent by weight ozoneconcentration to the ambient.

[0048] However, it will be understood that a skilled artisan wouldrecognize a wide variety of other types of ozone sources, filters,valves, heaters, and pumps could be advantageously employed in the ozoneshower system 15. For example, a skilled artisan would recognize thatthe pump 40 could be a centrifuge pump. Moreover, the heater 45 could bea heat exchanger. In addition, the valves could be two-way valves. Thefilter 55 could be a charged particle filter. The ozone source could bean electrolytic type generator.

[0049]FIG. 3 illustrates one embodiment of the process chamber 20. Theprocess chamber 20 includes the chamber lid 25 covering the full chamber30 and the short chamber 35. As shown in FIG. 3, the full chamber 30 andthe short chamber 35 are separated by a wall 68. The wall 68 has aheight less than that of the full chamber 30 such that a space existsbetween the top of the wall 68 and the chamber lid 25.

[0050] Moreover, according to this embodiment, the chamber lid 25includes a water manifold 70 having an array of spray nozzles 75. Thespray nozzles 75 are configured such that when the chamber lid 25 coversthe full chamber 30 and the short chamber 35, the spray nozzles 75extend above the full chamber 30. The full chamber 30 holds wafers 80 ina cassette 85. The cassette 85 rests on a stand 90. The stand 90, inturn rests on the bottom of the full chamber 30. A pump pool 95 fillsthe bottom of the full chamber 30 to a height less than that of thestand 90 such that the pump pool 95 does not reach the cassette 85 orthe wafers 80. In addition, a diverted pool 98 fills the short chamber35.

[0051] According to one embodiment, the spray nozzles 75 in the spraylid 25 are cone spray nozzles commercially available from Santa ClaraPlastics. However, it will be understood that a skilled artisan wouldrecognize that a wide variety of the spray nozzles 75 could be used inthe chamber lid 25. For example, the chamber lid 25 could employ showermassage nozzles, knife-edge nozzles, or the like.

[0052] Moreover, according to one embodiment of the invention, the spraynozzles 75 attach to the water manifold 70 such that when activated, asubstantially uniform water boundary layer forms on each of the wafers80.

[0053] According to one embodiment, the cassette 85 holds 13 of thewafers 80 and is commercially available from Santa Clara Plastics.However, it will be understood that a skilled artisan would recognizethat a wide variety of cassettes or other devices could be used to holda wide number of the wafers 80. For example, the number of the wafers 80for a given cassette is often simply vendor dependent. Moreover, thecassette 85 may be altogether avoided and the process chamber 20 couldemploy robot arms or the like. A robot arm for holding and exchangingthe wafers 80 is commercially available from Submicron Systems.

[0054]FIG. 4 illustrates an array of the spray nozzles 75 on the spraylid 25, according to one embodiment of the invention. FIG. 4 illustratesthe array comprising six rows and four columns. The six rows and fourcolumns are depicted from the perspective of the wafers 80 such that thewafers 80 align parallel to the rows. According to one embodiment, thespray nozzles 75 in the 6 rows are separated from each other by 1.75inches and the spray nozzles 75 in the 4 columns are separated from eachother by 2.5 inches. However, it will be understood that a wide varietyof patterns and distances could be used arrange the spray nozzles 75 inorder to provide the substantially uniform water boundary layer on thewafers 80.

[0055] According to this embodiment, the spray lid 25 further includesan ozone nozzle 100. For convenience, the ozone nozzle 100 and the spraynozzles 75 are the same, outside of the fact that the ozone nozzle 100does not connect to the water manifold 70. Rather, the ozone nozzle 100connects to the ozone source such that the ozone nozzle 100 suppliesozone into the ambient in the full chamber 30. Again, it will beunderstood that a skilled artisan would recognize a wide variety ofdevices and input areas where the ozone source could supply ozone to theprocess chamber 20. For example, the ozone nozzle 100 could be entirelydifferent from the spray nozzles 75 and enter the process chamber 20from a position other than the center of the array of the spray nozzles75. Furthermore, the chamber lid 25 could comprise multiple ozonenozzles 100 creating multiple entry points for the ozone into the fullchamber 30.

[0056] According to one embodiment, the ozone shower system 15 employsthe pulsing process 10 in order to decrease the time needed to stripphotoresist from the wafers 80. In Step S1, the ozone source of theozone shower system 15 pumps ozone into the full chamber 30 through theozone nozzle 100. According to this embodiment, the ozone concentrationis at least 13 weight percent. Further, the pump 40 begins pumping waterfrom the pump pool 95 through the heater 45. According to thisembodiment, the heater 45 heats the water to approximately 60-95° C. Thepump 40 then pumps the water though the filter 55 to removecontaminates. In Step S2, the selector valve 60 directs the now filteredheated water through the first path to the chamber lid 25 and the watermanifold 70. The water manifold 70 distributes the filtered heated waterto the array of the spray nozzles 75. The spray nozzles 75 spray thefiltered heated water on the wafers 80 such that the water sheets overthe photoresist, thereby forming the water boundary layer. As thefiltered heated water sheets off the wafers 80, it falls through oraround the cassette 85 and the stand 90 such that the filtered heatedwater collects in the pump pool 95. The selector valve 60 continues todirect the filtered heated water through the first path forapproximately 5 seconds.

[0057] In Step S3, the selector valve 60 redirects the filtered heatedwater into the second path, thereby shutting off the supply of water tothe spray nozzles 75. This redirection effectively deactivates the spraynozzles 75. The filtered heated water travels through the second path tothe short chamber 35 where it flows into the diverted pool 98. When thediverted pool 98 becomes deeper than the height of the wall 68, thefiltered heated water in the diverted pool 98 spills over the wall 68and into the pump pool 95 in the full chamber 30. The water spillingover the wall 68 does not touch or effect the wafers 80, rather, itsimply adds to the pump pool 95. The selector valve 60 continues todirect the filtered heated water through the second path for 20 seconds.

[0058] In Decision S4, the ozone shower system 15 determines whetherfive minutes has elapsed since first activating the pump 40. If so, thepump 40 shuts down. On the other hand, if 5 minutes has not elapsed, theselector valve 60 redirects the filtered heated water back through thefirst path and reactivates the spray nozzles 75, thereby restarting StepS2.

[0059] Using the selector valve 60 to redirect the filtered heated wateradvantageously makes continued starting and stopping the pump 40unnecessary. By using redirection, the pump 40 continues to pumpthroughout the ozone-photoresist reaction time. Furthermore, theemployment of the pump pool 95 advantageously ensures the pump 40 willnot run dry and allows for recycling of the filtered heated water.

[0060] As mentioned above, employing the pulsing process 10 in the ozoneshower system 15 advantageously reduces the time needed to stripsubstantially all the photoresist from the wafers 80. In addition, asmentioned above, the pulsing process 10 accomplishes this reductionwithout rotating the wafers 80 at high velocities. In fact, according toone embodiment, the wafers 80 are held stationary.

[0061] However, when the wafers 80 do not rotate, the water boundarylayer should be as uniform as possible. Thicker areas of the waterboundary layer can effect the ability of the water to transport thehighly concentrated dissolved ozone to the photoresist, thereby slowingthe stripping process. Typically, the water boundary layer may vary inthickness in at least two places. First, the cassette 85 typically usestwo horizontal rods contacting the wafers 80. The surface tension of thehorizontal rods contacting the wafers 80 tends to thicken the waterboundary layer in those areas. Second, gravity can cause the waterboundary layer to “channel” towards a point near the bottom of thewafers 80, thereby thickening the water boundary layer in that area aswell.

[0062] Therefore, according to one embodiment of the invention, theozone shower system 15 slowly rotates the wafers 80 in order increaseuniformity of the water boundary layer. For example, FIG. 5 illustratesa side view of the wafer 80 and the cassette 85. The cassette 85includes a portion 87 that holds each wafer 80. The portion 87 could bethe above-mentioned horizontal rods, or as shown in FIG. 5, the portion87 could comprise a concave slot substantially matching the curvature ofthe bottom of the wafer 80. Each concave slot could correspond to eachwafer 80 in the cassette. As illustrated in FIG. 5, when the wafers 80are to be rotated, two rotating axles 120 contact the wafers 80. Asshown, the two rotating axles 120 substantially support the wafers 80allowing for a gap 125 to exist between the cassette 85 and the wafers80.

[0063] According to one embodiment, the two rotating axles 120 rotate inthe one direction such that the wafers 80 rotate in the other. Forexample, as shown in FIG. 5, the two rotating axles 120 rotate to theleft, thereby rotating the wafers 80 to the right. However, it will beunderstood that a wide variety of rotating mechanisms could be used torotate the wafers 80. For example, when the cassette 85 includeshorizontal rods to support the wafers 80, those horizontal rodsthemselves could be rotated.

[0064] According to another embodiment, the two rotating axles 120rotate the wafers 80 at velocities ranging from about 100 revolutionsper minute (rpm) to stationary. According to one embodiment, the tworotating axles 120 rotate the wafers 80 at approximately 3 rpm.

[0065] The slow rotation of the wafers 80 changes both the area wherethe cassette 85 contacts the wafers 80, and which area of the wafers 80comprises the bottom. Therefore, by slowly rotating the wafers 80, theozone shower system 15 advantageously provides a more uniform waterboundary layer. Through the more uniform water boundary layer, the ozoneshower system 15 provides efficient transport of highly concentrateddissolved ozone to the photoresist on the wafers 80. The efficienttransport dramatically reduces the processing time for theozone-photoresist reaction, thereby increasing semiconductor processflow efficiency. Also, slow rotation of the wafers 80 avoids themechanical complexity and risk of damage associated with very highrotation velocities.

[0066] Although one embodiment of the ozone shower system 15 employsslow rotation of the wafers 80, it will be understood that a skilledartisan would recognize a wide variety of other ways to create uniformwater boundary layers. For example, the ozone shower system 15 couldemploy rotating spray nozzles 75 that correct for channeling and gravityproblems. According to another embodiment, the ozone shower system 15could aim the spray nozzles 75 such that the water spray contacts thewafers 80 in a manner that causes a slow rotation. For example,knife-edge spray nozzles could provide a spray that contacts only oneside of the each wafer 80, thereby slowly rotating the wafer inside thecassette 85. Such an embodiment avoids the use of the two rotating axles120.

[0067] On the other hand, the ozone shower system 15 could employtipping mechanism that tips the wafers 80 from side to side in order tocreate uniform water boundary layers. Further, the ozone shower system15 could employ non-mechanical means to combat non-uniformity. Forexample, surfactants, acid spiking, water vapor, heated workpiece, andvery hot water could also be included to help improve theozone-photoresist reactions.

[0068] Although the foregoing invention has been described in terms ofcertain preferred embodiments, other embodiments will be apparent tothose of ordinary skill in the art. For example, the ozone could also bepulsed into the process chamber 20 and the ozone pulse could also have alimited duty cycle. Additionally, other combinations, omissions,substitutions and modification will be apparent to the skilled artisan,in view of the disclosure herein. Accordingly, the present invention isnot intended to be limited by the recitation of the preferredembodiments, but is instead to be defined by reference to the appendedclaims.

What is claimed is:
 1. A method for stripping a layer from asemiconductor wafer, the method comprising: introducing ozone into aprocess chamber; activating a water spray for a first predeterminedamount of time, thereby creating a water layer over a layer of asemiconductor wafer, wherein the water layer transports highconcentrations of the ozone to the semiconductor wafer; deactivating thewater spray for a second predetermined amount of time, therebycontrolling a thickness of the water layer; and re-activating andre-deactivating the water spray until the ozone substantially removesportions of the layer from the semiconductor wafer.
 2. The methodaccording to claim 1 , further comprising holding the semiconductorwafer stationary.
 3. The method according to claim 1 , furthercomprising slowly rotating the semiconductor wafer.
 4. The methodaccording to claim 1 , wherein the first predetermined amount of time isapproximately five seconds.
 5. The method according to claim 1 , whereinthe second predetermined amount of time is approximately twenty seconds.6. An ozone shower system, comprising: an ozone source configured tosupply ozone to a process chamber; a sprayer connected to a fluid sourcesuch that fluid sprays over a workpiece in the process chamber; a pumpconnected to the fluid source; and a selector valve connected to thepump, the selector valve configured to selectively pulse the fluidthrough the sprayer.
 7. The ozone shower system of claim 6 wherein theworkpiece is a semiconductor wafer.
 8. The ozone shower system of claim7 further comprising a cassette that holds a plurality of semiconductorwafers.
 9. The ozone shower system of claim 8 wherein the cassette isconfigured to rotate.
 10. A method comprising: introducing a reagent toan ambient; activating a solution spray in the ambient for a first timeperiod; and deactivating the solution spray for a second time period,thereby increasing the efficiency of a reaction of the reagent and aworkpiece.
 11. The method of claim 10 further comprising repeating theactivating and deactivating of the solution spray.
 12. The method ofclaim 10 , further comprising rotating the workpiece.
 13. The method ofclaim 10 , wherein the ratio of the first time period over the firsttime period added to the second time period ranges from 3% to 97%. 14.The method of claim 10 , wherein the ratio of the first time period overthe first time period added to the second time period is approximately20%.
 15. A reaction chamber comprising: a gas input; a plurality ofnozzles connected to a nozzle manifold; a wafer cartridge holdingwafers; a first fluid line connected to the nozzle manifold; and asecond water line configured to divert water flow away from the firstfluid line.
 16. A reaction chamber comprising: at least one nozzleconnected to a fluid supply and configured to pulse fluid onto aworkpiece; and a rotator wherein the rotator rotates the workpiece at avelocity ranging from approximately 100 rpm to stationary.
 17. Anapparatus comprising: at least one wafer processing chamber wherein anozone rich environment exists within the wafer-processing chamber; asprayer; and a pulsating fluid source, the pulsating fluid sourceconfigured to pulse a solution through the sprayer into the ozone richenvironment.
 18. The apparatus of claim 17 wherein the solution is ozonerich.
 19. The apparatus of claim 17 wherein the solution combines withthe ozone in the ozone rich environment.
 20. The apparatus of claim 17wherein the sprayer comprises a plurality of spray nozzles.
 21. Theapparatus of claim 17 wherein the pulsating fluid source is configuredto pulse at approximately two pulses per minute.
 22. The apparatus ofclaim 17 wherein the pulsating fluid source is configured to pulse atapproximately one pulse every two seconds.
 23. The apparatus of claim 17wherein the pulsating fluid source is configured to pulse at range fromapproximately one pulse every two seconds to approximately five pulsesvery minute.
 24. The apparatus of claim 17 wherein the pulsating fluidsource has a 50% duty cycle.
 25. The apparatus of claim 17 wherein thepulsating fluid source has an 8% duty cycle.
 26. The apparatus of claim17 wherein the pulsating fluid source have a duty cycle the varies from3% to 97%.
 27. An apparatus comprising: at least one semiconductorprocessing chamber; and a pulsating fluid source, the pulsating fluidsource configured to pulse an ozone-rich solution into thesemiconductor-processing chamber.
 28. The apparatus of claim 27 whereinthe ozone-rich solution further combines with ozone in the semiconductorprocessing chamber.
 29. The apparatus of claim 27 further comprising aspray nozzle that directs the pulsating fluid into thesemiconductor-processing chamber.
 30. The apparatus of claim 27 whereinthe pulsating fluid source is configured to pulse at approximately twopulses per minute.
 31. The apparatus of claim 27 wherein the pulsatingfluid source is configured to pulse at approximately one pulse every twoseconds.
 32. The apparatus of claim 27 wherein the pulsating fluidsource is configured to pulse at range from approximately one pulseevery two seconds to approximately five pulses very minute.
 33. Theapparatus of claim 27 wherein the pulsating fluid source has a 50% dutycycle.
 34. The apparatus of claim 27 wherein the pulsating fluid sourcehas an 8% duty cycle.
 35. The apparatus of claim 27 wherein thepulsating fluid source have a duty cycle the varies from 3% to 97%. 36.A method comprising: introducing a reagent into an ambient; and pulsinga solution spray in the ambient, thereby increasing the efficiency of areaction of the reagent.
 37. The method of claim 36 further comprisingdirecting the pulsating solution spray onto a workpiece.
 38. The methodof claim 36 further comprising directing the pulsating solution sprayonto a wafer.
 39. The method of claim 36 further comprising directingthe pulsating solution spray onto a wafer during a first time period.40. The method of claim 39 further comprising rotating the wafer duringat least a portion of the first time period.
 41. An ozone shower systemcomprising: a process chamber; and a pump, connected to the processchamber and configured to pulse a solution into the process chamber. 42.The ozone shower system of claim 41 , wherein the pulse of the solutionlasts approximately five seconds.
 43. The ozone shower system of claim41 , wherein the pump activates and deactivates to create the pulse. 44.The ozone shower system of claim 41 , wherein the pump further comprisesa switching mechanism to create the pulse.
 45. The ozone shower systemof claim 44 , wherein the switching mechanism comprises a deviceconfigured to divert the solution from one area of the process chamberto another area of the process chamber.
 46. An apparatus comprising apulsator that pulses a solution into an ozone-rich environment to createan ozone-rich solution.
 47. The apparatus of claim 46 wherein thepulsator is a spray nozzle.
 48. The apparatus of claim 46 wherein thesolution is water.
 49. The apparatus of claim 46 wherein the temperatureof the solution ranges from approximately 20° C. to approximately 95° C.50. The apparatus of claim 46 wherein the temperature of the solutionranges from approximately 60° C. to approximately 95° C.
 51. Theapparatus of claim 46 wherein the temperature of the solution is lessthan approximately 20° C.
 52. The apparatus of claim 46 wherein thetemperature of the solution is greater than 95° C.
 53. The apparatus ofclaim 46 wherein the ozone-rice environment is within a semiconductorprocessing chamber.
 54. An apparatus comprising: a rotating platformthat is configured to rotate a workpiece; and a pulsator that pulses asolution into an ozone-rich environment to create an ozone-rich solutionon the workpiece.
 55. An apparatus comprising a sprayer thatperiodically pulses an ozone-rich solution onto a wafer.
 56. Theapparatus of claim 55 wherein the pulsator is a spray nozzle.
 57. Theapparatus of claim 55 wherein the solution is water.
 58. The apparatusof claim 55 wherein the temperature of the solution ranges fromapproximately 20° C. to approximately 95° C.
 59. The apparatus of claim55 wherein the temperature of the solution ranges from approximately 60°C. to approximately 95° C.
 60. The apparatus of claim 55 wherein thetemperature of the solution is less than approximately 20° C.
 61. Theapparatus of claim 55 wherein the temperature of the solution is greaterthan 95° C.
 62. An apparatus comprising: a rotating platform that isconfigured to rotate a workpiece; and a pulsator that pulses anozone-rich solution on the workpiece.